(a) Technical Field
The present disclosure relates to a method for manufacturing a manifold for a fuel cell. More particularly, it relates to a method for manufacturing a manifold for a fuel cell with a multilayer structure in which a plurality of individual manifolds are stacked and bonded together.
(b) Background Art
In general, a manifold for a fuel cell consists of many internal paths (or flow fields) including inlet paths and outlet paths for supplying hydrogen, air, and coolant to a fuel cell stack as an electricity generation source.
In order to integrate these internal paths, several structures having internal paths are stacked and bonded together.
FIG. 1 is a schematic diagram showing a conventional individual manifold for a fuel cell, and FIG. 2 is a schematic diagram showing a conventional manifold for a fuel cell.
Conventionally, in order to form a manifold 10 for a fuel cell into a multilayer structure, a plurality of individual manifolds 11 each having individual paths 11a on upper and lower surfaces are prepared as shown in FIG. 1. An adhesive is applied to path-processed surfaces (i.e., the upper and lower surfaces on which the individual paths 11a are formed) of each of the individual manifolds 11. The individual manifolds 11 are compression-bonded together, and when the adhesive is cured, the adhesive exposed to the outside of the manifold 10 is removed, thus forming the manifold 10 shown in FIG. 2.
However, the above-described method for manufacturing the manifold for the fuel cell has a number of problems.
First, due to the difference in properties between the materials for the manifold and the adhesive, a difference in volume change between the different materials occurs under environmental conditions of an actual vehicle, which degrades the adhesive. As a result, the integrity of the airtight seal of the bonded portions is broken upon long-term operation, resulting in deterioration of the durability of the manifold. As such, foreign materials may enter the internal paths 12 of the manifold as shown in FIG. 2.
For example, foreign materials may include ionic impurities which move along the flow path of coolant, and may increase electrical conductivity to cause an insulation problem. These impurities may also clog the internal paths 12 to cause a degradation in performance.
Second, although the adhesive distributed on the outer surface of the manifold is removed and subject to ultrasonic cleaning after the compression bonding, some adhesive material in the bond may be dislodged or separated during use of the fuel cell and gradually cause build up in the internal paths 12 over time.
Third, the conventional manifold for the fuel cell is formed of epoxy glass and is manufactured under processing conditions where high-speed rotation and low-speed movement are inevitable due to the nature of the material. Moreover, it may take 20 days or longer to manufacture a single manifold due to the complex and variable shape of the manifold, as well as the above-described processing conditions.
Accordingly, since the internal paths of a conventional manifold for the fuel cell require a long time to process, an additional process for reducing the weight of the fuel cell would be cost prohibitive. Moreover, even if the manufacturing time was not an issue, it would still be difficult to reduce the weight due to the high brittleness of the fuel cell manifold material.
Fourth, due to the nature of the epoxy glass material, manufacturing a fuel cell manifold by a wet process is problematic due to moisture absorption. Thus, the manifold is manufactured by a dry process, which generates a large amount of fine powder, which can create harmful environments that threaten workers' health.
The above information disclosed in this Background section may be used for enhancement of understanding of the background of the disclosure.